As a conventional technique of operating plural power converters in parallel to supply the power to a load, the technique disclosed in Patent Literature 1 is given as an example. In this technique, to suppress the current concentration on a particular one of plural power supply circuits operating in parallel, the respective power supply circuits are controlled to balance their output currents.
Also, when a battery such as a lithium ion battery is charged with the use of the power converter conventionally, the power converter performs in an order of a constant current charging operation and a constant voltage charging operation (for example, see Patent Literature 2). Alternatively, the power converter performs in an order of the constant current charging operation, a constant power charging operation, and the constant voltage charging operation (for example, see Patent Literature 3).
Here, as illustrated in FIG. 10, the constant current charging operation is a charging operation with a charging current Iot being constant, and the constant power charging operation is a charging operation with a charging power (Pout=Vout×Iot) being constant. In addition, the constant voltage charging operation is a charging operation with a charging voltage Vout being constant. In other words, after the charging starts, the charging operation is performed efficiently in the order of the constant current charging operation and the constant power charging operation, and the charging operation is performed up to immediately before a limit value of the battery capacity while avoiding overcharging by performing the constant voltage charging operation at the end stage of charging.